How strictly should speed limits be enforced?

I’m thinking of the two-lane country road, one lane in each direction. If there’s a solid yellow line on my side it’s not legal to pass; however, if there is a dashed line it is (potentially) legal to pass you; obviously, the trailing car needs to look up the road to confirm there are no oncoming vehicles because then it wouldn’t be safe to pass but if you encounter a dashed line & there are no oncoming vehicles in sight then get on the gas & pass the car in front of you.
If the passed vehicle is doing 52 & the passing one is at 65 the passer is in the oncoming lane a lot shorter of a time than if they only pass the slower one at 55.

If there’s nothing coming, there’s probably no need to pass at a speed above the limit.
If there might be something coming the other way that you would hit unless you pass by speeding, it’s probably not safe to pass at all (you are, by accelerating, closing that distance faster).
If the speed differential between the vehicles is very small (you’re talking about 2mph difference - which could be within the scope of speedometer calibration of the two vehicles), there’s probably no pressing need to pass.

We have similar road markings here indicating when overtaking is and is not permitted. A dashed line permitting overtaking does not very often (in my experience) indicate that it is actually safe to overtake - in the same way that a 60mph speed limit does not necessarily mean it is safe to drive at that speed on all stretches of that road.

It may be more complex than this; certainly a 50mph vehicle overtaking a 30mph vehicle spends less time passing than if the speed differential were smaller, but the faster you travel when overtaking, the faster you close the distance between yourself and any unanticipated or unseen hazard - giving yourself less time to react (or to put it another way, the faster you consume the free space you initially saw before overtaking) - so it’s not a simple case of exchanging likelihood for severity on one risk, it also creates a new risk with its own independent ratings of likelihood, albeit with perhaps shared severity.

No, it exchanges some risks for other risks.

What it does is increasing the real risk (speed difference between you and oncoming traffic)!to lessen the perceived risk (time spent in the left lane).
It is an illustration of how we suck at risk management.

Both those risk factors are equally real. As I outlined.

Absolutely false! As I stated above, most passing zones are relatively short before you come to the next curve or hill in the road which obstructs your view of what’s oncoming beyond them.
If I have a legal passing zone that is ¼ mile long I can’t pass you in that area by only going one or two mph faster than you as that will take almost a minute & therefore most of a mile to pass you.

There may or not my not be another vehicle coming for another 5 mins or even an hour; however, I can only see up the road as far as the next curve or hill & not beyond that.

The end of your overtake is the risky part. If the distance you can see, and the distance you have in which to overtake are both limited and relatively short, arriving at the end of that distance at high speed, on the wrong side of the road, is risky.

I concede there are undoubtedly cases where the various factors involved are such that a speeding-overtake is possible and safe, where a speed-observing overtake is simply not possible. I don’t doubt such cases exist.
I do doubt they are the majority of cases, but this view is based on experience of roads here, many of which were made at a time when horses were the fast way to get about (the road surfaces and often the road width have been updated - the routes, junctions, corners etc have not)

I assume that, in a place where passing is permitted, highway engineers (or whoever) have determined that there is, at least theoretically, enough time to safely pass another vehicle if no oncoming traffic is visible. Which makes me wonder (and this may well be a Factual Question) how much time they allow for a passing maneuver in making such a determination, and how much of a speed differential that time corresponds to.

I more or less generally drive slightly faster than the speed limit, considering road conditions- when we have heavy rain, I slow down to below the speed limit. If I was driving in bad conditions but had a line of cars behind me, I would use a turnout to let them pass. In fact, I generally do pull over to let faster drivers pass, unless they tailgate too closely.

I figured it was in MUTCD; just had to find the right section, & it’s distance, not time.

I was assuming good conditions for this discussion, dry, daylight, not driving into a low sun, etc.

You need to divide by 1.609 to covert from fatalities per mile to fatalities per km so
Converting the US number to the same units as the Italian number say that’s 1.10 * 10 / 1.609 = 6.83 per billion km so slightly less than the rate in Italy.

The Librarian might have been looking at this link which had the Italian death rate at 5.2/100,000 inhabitants compared to 12.9 in the USA. (and has no data for the Italian deaths per Bn km). Interestingly the wiki page you posted gives the Italian death rate as 9.4/100,000 inhabitants.

D’oh. Thank you. The difference between multipyling vs dividing by 1.609 is significant.